Avaaz, an online activist group, created the campaign targeting Rubio, which also was spotted rolling through downtown Miami and Little Havana.

“Florida has notoriously lax gun laws, and Rubio, who is supported by the NRA, has never attempted to reform them,” Emma Ruby-Sachs, Avaaz’s deputy director said. “The senator ranks as one of the highest recipients of NRA contributions and has received an A+ rating from the NRA.”

A person who answered the phone Friday at Rubio’s Miami-area office declined to comment on the billboards.

Added Ruby-Sachs: “Today citizens are asking: How come Rubio refuses to protect our children? The senator has taken fire across the country for his toothless response to the shooting, calling it ‘inexplicable’. We called (that) ‘inexcusable.'”